1. Field of the Invention
The present invention relates to a method for monitoring functional components of a motor vehicle, including an internal combustion engine, an exhaust system having a manifold, catalytic converter, diesel particulate filter, front muffler, mid muffler, rear muffler, exhaust pipes and/or tailpipe, and an intake system having an intake muffler and/or intake pipes.
2. Description of the Background Art
Known from WO 98/01 728, which corresponds to U.S. Pat. No. 6,347,285, is a device for detecting analog measurement signals for the acoustical diagnosis of test pieces. In this process, analog measurement signals from a test piece can be recorded with the aid of vibration transducers. A computer is equipped with a standard interface card that serves to digitize the measurement signals. A switching signal is used to produce a carrier signal that can be input through an interface that is preferably serial. A control program in the computer switches the input of measurement signals on and off by means of the carrier signal.
DE 42 07 728 A1 describes a method for quality testing of test objects wherein the test objects to be examined are excited into emitting sound waves by an external pulsed excitation, wherein the emitted sound waves are detected in a sound detector, and wherein a sorting of the test objects into at least two quality classes takes place based on the detected sound. In this context, the classification of the sound spectrum of the test objects takes place through a neural network.
DE 40 17 448 A1 describes a method for diagnosing the mechanical characteristics of machines in which rotating components that cause vibrations are present. In order to produce a rapid and reliable method with which routinely acquired vibration patterns can be processed to diagnose typical machine defects, the detection signal is transformed from the time domain into the frequency domain by a frequency transform method, and the investigation of the signal is performed in the frequency domain.
Known from WO 96/13 011, which corresponds to U.S. Pat. No. 5,602,757, is a vibration monitoring system for a machine, which includes a microcontroller and a machine that is to be monitored. The machine includes at least one rotating element and at least one sensor for converting mechanical vibrations of the machine into a corresponding electrical signal that is analyzed by the microcontroller.
U.S. Pat. No. 5,109,700 describes a method and an apparatus for analyzing rotating machines. Here, a vibration transducer connected to a rotating machine senses the vibration of the machine and generates a corresponding electrical output signal. The apparatus is provided for analyzing the electrical signal and for outputting or representing the signal level, the rotational speed, and the condition of the bearing of the machine.
DE 198 31 457 A1 describes an after-market device for detecting the exhaust gas composition in motor vehicles that are not equipped with OBD technology as standard equipment. If an assembly that is to be monitored fails or has a malfunction, a signal light on the dashboard is activated and is stored as a failure rate. The identified malfunction can be read out at a later time through a standardized interface in a workshop for identification and correction of the failure, for example.
In the engine operating system according to DE 199 16 927 A1, which corresponds to U.S. Pat. No. 6,076,348, the signal from a sensor in the exhaust pipe is used within a feedback loop for controlling the air/fuel ratio in the combustion chamber. To this end, the signals of the exhaust gas component sensor are statistically analyzed by the motor controller and are processed for controlling the fuel delivery system. In this way, near-real-time feedback is achieved between the actual state and the exhaust gas aftertreatment device and the technical causes thereof.
Regardless of whether the diagnostic parameters determined by means of OBD are used immediately or not used until a later time, it is always necessary to evaluate these parameters. The critical point is an assessment of whether the parameters characterize a correct state or a faulty state. The OBD system typically has a preprogrammed characteristic curve, which is used as a basis for comparison for the later on-board measurement and off-board measurement. Especially for low-emissions concepts with correspondingly low OBD thresholds, a very precise distinction between the states “OK” and “not OK” is necessary. Statistical methods are a suitable solution option for this.
Statistical methods for evaluating diagnostic results are known in principle, wherein the method of classification is already in use in connection with OBD. Thus, for example, classification memories are present in prior art OBD control units, making it possible to first standardize the diagnostic results by means of a normalization function and then count them by classes. Another function is to store minimum or maximum diagnostic results by classes as a function of a characteristic diagnostic parameter.
Using the OBD method described in DE 44 34 197 C2, the condition of assemblies can also be diagnosed. Sensors which are in operative connection with the electronic engine control system are arranged on the assemblies to be monitored. The signal parameters of these sensors are first standardized by means of a normalization function. For this purpose, classifiers are proposed that can take the form of fixed classifiers for simple applications. Preferably, this diagnostic technique is based on trainable classifiers, which are trained or characterized using reference sensors with known operating characteristics or on the basis of statistically determined parameters. In this connection, multiple executions of decision loops may be necessary before a functional trainable classifier is produced. The diagnostic results are assigned to the classes of a classification memory on the basis of the standardization achieved by the normalization function. Next, using an evaluation function, it is possible to draw a conclusion regarding the condition of the monitored assemblies on the basis of the class assignments, in which either “OK” or “not OK” is determined in particular by comparison with a threshold value. This method is fundamentally suited for on-board diagnostics of motor vehicle assemblies that are relevant to emissions. In this context, the generation of the trainable classifiers by comparison of signal parameters to be normalized with stored, statistically determined signal parameters advantageously reduces development and test effort for the rules required to classify the sensors. However, it is disadvantageous that only a small number of classes can be implemented in the classification memory. A precise decision between the evaluations “OK” and “not OK” is thus questionable. Additional uncertainties with regard to the evaluation to be made are created by random dispersion of the diagnostic results. According to the disclosure in this document, preferably three classes are available in the classification memory, which, for example, characterize a fuel/air mixture in the states “rich/normal/lean”. While this is indeed adequate for use in exhaust gas sensors, more classes have to be available for further differentiation or for other assemblies.
DE 101 55 647 A1discloses an OBD method that makes possible an improved analysis of the diagnostic parameters. This is achieved, in particular, by the means that an adequately large number of classes is assigned in a classification memory, and thus an essentially exact evaluation of the state of the assemblies to be monitored is achieved. In addition, each class of the classification memory is assigned a weighting factor.
Finally, DE 39 32 436 A1, which corresponds to U.S. Pat. No. 5,072,391, discloses a diagnostic system for fault diagnosis in an electronic control unit in a motor vehicle, in which the electronic control unit has sensors and measurement devices for detecting various operating states in the motor vehicle and has a first memory device for storing the data supplied by the sensors and measurement devices. The diagnostic system also includes a diagnostic device with a control section in which a second memory device is provided for storing diagnostic programs for fault diagnosis in the electronic control unit. Also provided are a display element for displaying the diagnostic data, a keyboard for entering a diagnostic operating mode in the control section, and a device for connecting the diagnostic device to the electronic control unit. A second memory device for storing diagnostic programs for diagnosis of the electronic control unit is provided in the diagnostic device, and a third memory device for storing diagnostic programs for diagnosis of the electronic control unit is provided in the electronic control unit. Located in the diagnostic device is a designating unit for selective assignment of relevant primary and secondary functions to the electronic control unit and diagnostic device to produce a system with master devices and slave devices. A device for fault diagnosis in accordance with the diagnostic programs stored in the memory device in master mode is provided in the electronic control unit.
It is known that motor vehicles, especially those with internal combustion engines, contain a great number of components that during operation are subjected to greater or lesser loads and greater or lesser wear. Thus, for example, the internal combustion engine may run unevenly because the ignition is misadjusted, because the valves are misadjusted, because the fuel quality is incorrect, because the engine is being operated in the wrong load range, because a bearing is bad, because the intake system and/or the exhaust system are clogged or damaged, etc. The exhaust system is subject to wear caused by the high temperatures of the exhaust gases, the pulsations of the exhaust gases, the oscillations and vibrations caused by driving, and corrosion. This can cause damage to pipes and housings, damping material located in the muffler can be blown out, diesel exhaust particulate filters can be overloaded or clogged, catalytic converters can be destroyed, etc.
The intake system of the motor vehicle is also subject to wear. Likewise subject to wear is the auxiliary equipment found in motor vehicles, from the generator to the air conditioning system.